The number oftotal and viable cells was determined with a hemocytometer by using the methylene blue staining method (9). The concentration of ethanol was determined by gas chromatography using isopropanol as an internal standard, as described pre viously (18)-The residual sugar concentration was measured using the F-kit (Roche, Basel, Swi tzerlana). according to the manufacturer's instructions. Organic acids were analyzed by a post-label method using a HPLC system equipped with a UV detector (at 450 nm) and a Shimpack SCR-101H column (Shimadzu, kyoto, Japan), as described previously (21 ).